User`s manual

TN-5516/5518 Series Featured Functions
3-41
Traffic Queues
The TN-5500 hardware has multiple traffic queues that allow packet prioritization to occur. Higher priority
traffic can pass through the TN-5500 without being delayed by lower priority traffic. As each packet arrives in
the TN-5500, it passes through any ingress processing (which includes classification, marking/re-marking),
and is then sorted into the appropriate queue. The switch then forwards packets from each queue.
The TN-5500 supports two different queuing mechanisms:
• Weight Fair: This method services all the traffic queues, giving priority to the higher priority queues. Under
most circumstances, this method gives high priority precedence over low-priority, but in the event that
high-priority traffic except the link capacity, lower priority traffic is not blocked.
• Strict: This method services high traffic queues first; low priority queues are delayed until no more high
priority data needs to be sent. This method always gives precedence to high priority over low-priority.
Configuring Traffic Prioritization
Quality of Service (QoS) provides a traffic prioritization capability to ensure that important data is delivered
consistently and predictably. The TN-5500 can inspect IEEE 802.1p/1Q layer 2 CoS tags, and even layer 3 TOS
information, to provide a consistent classification of the entire network. The TN-5500’ QoS capability improves
your industrial network’s performance and determinism for mission critical applications.
QoS Classification
The TN-5500 supports inspection of layer 3 TOS and/or layer 2 CoS tag information to determine how to
classify traffic packets.